The present invention generally relates to an optical recording and reproducing apparatus provided with a focus drawing-in function, a function of detecting the reverse insertion of a recording medium having of a multilayer recording membrane or an AGC circuit function corresponding to a multilayer recording membrane on the inner periphery and the outer periphery of the recording medium from the same layer direction during recording and reproducing one a recording medium having a multilayer recording membrane.
One embodiment of the conventional optical recording and reproducing apparatus will be described hereinafter with reference to the drawings. FIG. 4 is a block diagram showing the basic construction of the conventional optical recording and reproducing apparatus. In FIG. 4, reference numeral 1 denotes an optical disk used as a recording medium, and reference numeral 2 denotes a disk motor for rotating the optical disk 1. Reference numeral 3 denotes an optical head for recording signals on an optical disk with a laser and for also reproducing signals recorded on the optical disk 1. The optical head is composed of a semiconductor laser, an optical system, an object lens, a driving actuator comprising an object lens driving means, a focus error detecting system comprising a focus error detecting means, a tracking detecting system for detecting the errors of the laser spot and the tracking position, and a signal detecting system. The optical beams transmitted from the above described semiconductor laser are focused with an object lens, reach the optical disk recording membrane face where the reflected optical beams reach an optical detector for error detection use. In the optical detector, the lag in the focus direction and the lag in the tracking direction are detected, and the object lens is driven by an actuator so as to correct the lag in each direction within the given value. Reference numeral 4 denotes a linear actuator which is composed of a carriage on which the optical head 3 is mounted, a coil, a magnet, a yoke and a rail for carriage use. The linear actuator 4 moves the optical head 3 to a target position in a diametrical direction of the optical disk 1. Reference numeral 5 denotes an amplification circuit for amplifying the output signals from the signal detecting circuit of the optical head 3; reference numeral 6 denotes a semiconductor laser driving circuit used as a laser control circuit; reference numeral 14 denotes an amplification circuit used for focus error detection; reference numeral 15 denotes an amplification circuit for amplifying the output signals from the optical detector and used for tracking error detection; reference numeral 7 denotes a circuit used for groove sectional detection, which is adapted to operate a linear actuator after the focus drawing-in completion so as to detect the groove sectional signal. With a change-over switch 17 of the S-character drawing-in circuit and a focus control circuit after the detection, the switching operation is effected to the focus control circuit. Reference numeral 8 denotes a disk motor driving control circuit. Reference numeral 9 denotes a signal processing circuit which is adapted to feed a reproduction signal of the information pit from the optical head 3 amplified by the amplification circuit 5 of the signal detecting circuit, as a binary data, to the driving control circuit 13. During recording, the output of the laser light is applied to the disk face of the optical disk 1 in accordance with the signal from the driving control circuit 13 to be described later in a recording power mode so as to form a string of information pits on the recording face. Also, during reproduction, the existence and absence of the information pits can be read by the amount of optical reflection with the output of the laser beams being in a reproduction power mode. Reference numeral 10 denotes a driving circuit of the linear actuator 4 wherein the high speed movement of the optical head 3 to the target position is controlled by a position signal and by a speed signal detected by the optical detector of the optical head 3. Reference numeral 11 denotes a focus control circuit, and reference numeral 12 denotes a tracking control circuit. Reference numeral 16 denotes an S-character comparator circuit for use during the focus drawing-in operation time.
The above described driving control circuit 13 receives the instructions from the controllers of the above described respective control circuits and so on to execute and control the respective operations and to input execution commands to the respective controllers.
The optical operation of the recording and reproducing apparatus constructed as described hereinabove is described hereinafter. First, a disk 1 is engaged on a disk motor 2. The instructions from the driving control circuit 13 control the rotational speed of the disk motor 2 so as to be at a constant rate. The semiconductor laser of the optical head 3 is controlled by the semiconductor laser driving circuit 6 with the instructions from the driving control circuit 13. Further, the focus drawing-in operation is effected with the instructions from the driving control circuit 13. In the focus drawing-in operation, the focus control circuit is operated with the instructions from the driving control circuit 13 so as to drive the lens vertically, so that the focus error signals are formed with the light reflected from the disk recording face. Namely, the S-character curves of the focus error signal are outputted with the recording face being provided within the focus depth of the laser beam. The focus is detected from the focus error signal using the comparator circuit 16. Thereafter, the linear actuator 4 is driven into the inner periphery or the outer periphery with instructions from the driving control circuit 13 so as to detect the tracking error signal (groove sectional signal) using the groove sectional detecting circuit 7. Thereafter, the detected information is fed to the driving control circuit 13. Then, by the driving control circuit 13, a focus drawing-in change-over switch 17 is turned off to operate the focus servo system. Then, the control in the tracking direction is effected by the tracking control circuit 12. The feeding operation of the optical head 3 at this time is effected by a driving circuit 10 using the linear actuator 4. After the focus, tracking control operation is effected by the focus control circuit 11 and the tracking control circuit 12, the detected signal is amplified by the amplification circuit 5 of the signal detecting circuit and is fed to the signal processing circuit 9 where it is changed into a binary signal by the signal processing circuit 9 and is fed to the driving control circuit 13.
In the conventional construction as described hereinabove, when the laser is driven in the same laser direction during recording and reproducing on a recording medium having a multilayer record membrane, the focus error signal is outputted using the light reflected from the disk recording face during the focus drawing-in operation time, so that it is impossible to detect the position of the given recording membrane which is to be recorded or reproduced. Thus, during the recording and reproducing on the recording medium having a multilayer recording membrane, there is a problem in that the position of the given recording membrane cannot be ascertained.